The present invention relates to a selector pen, and more particularly to a selector pen for touch screen that has a structurally simplified switch and could be manufactured at lowered cost.
With the highly advanced computer technology, various kinds of electronic products have been developed to have compact volume and increased functions. For example, there are many applied electronic products having key-controlled functions directly provided on a screen thereof. The screen is provided with a sensing membrane via which user""s instructions are entered. Such screen is referred to as a touch screen and was originally developed for big-size screens for general computers but has currently been employed on small-size liquid crystal display (LCD) for electronic dictionary, personal digital assistant (PDA), etc. To enter instructions or to select options on the touch screen, a selector pen (that is, a light pen) is usually needed to touch the screen, though the instructions and the selections may also be entered by handwriting.
FIG. 1 is an exploded perspective view of a conventional selector pen 10. As shown, the selector pen 10 mainly includes a barrel 1, a transparent head 2, a light-emitting means 3, and a switch 4.
The barrel 1 is a hollow tube with the transparent head 2 fixedly connected to a front end thereof and the light-emitting means 3 mounted therein. A rear end of the barrel 1 is provided with an internal screw thread 11 for the switch 4 to screw thereinto.
The transparent head 2 is a substantially conic body having a blunt front point 21 and allows light emitted from the light-emitting means 3 inside the barrel 1 to pass therethrough.
The light-emitting means 3 includes a circuit board 31 having a light emitter 32, which is preferably a light emitting diode, connected thereto; a big spring 33 connected to a positive electrode of a power input of the circuit board 31; a small spring 34 connected to a negative electrode and located at a center in the big spring 33; and a battery 35 having a front outer peripheral surface forming a positive electrode to contact with the big spring 33 and a bar-shaped negative electrode forward projected from a center of the positive electrode to extend into the big spring 33 for contacting with the small spring 34. When a special light emitting diode is used, such as a white light emitting diode that needs a voltage higher than that for general light emitting diodes, the circuit board 31 is additionally provided with a voltage booster circuit 36, so that the voltage rises from low to high voltage to provide the special light emitting diode with normal working voltage.
The switch 4 includes a fixing seat 41, a movable rod 42, and a cap 43. The fixing seat 41 is a hollow tube generally divided into a lower half and an upper half. An upper outer periphery of the lower half is provided with a collar 411 having an outer diameter corresponding to that of the barrel 1, and a lower outer periphery of the lower half below the collar 411 is provided with an external screw thread 412 for engaging with the internal screw thread 11 of the barrel 1. The upper half of the fixing seat 41 is provided at an inner upper end with an internal screw thread 413. The movable rod 42 is provided around a lower portion of an upper half with an external screw thread 421 corresponding to the internal screw thread 413 of the fixing seat 41, immediately above the external screw thread 421 with a diameter-reduced gear 422, and above the gear 422 with a shaft 423. The cap 43 has an open lower end communicable with a stepped internal space defined by the cap 43. The stepped internal space of the cap 43 includes a first recess 431 most close to the open lower end for receiving the fixing seat 41 and the movable rod 42, a second recess behind the first recess for receiving the gear 432, and a third recess behind the second recess for receiving the shaft 433. The movable rod 42 is rotatably, upward and downward movably mounted in the fixing seat 41 through engagement of the external screw thread 421 with the internal screw thread 413.
When the light-emitting means 3 is mounted in the barrel 1, the light emitter 32 is caused to face forward and contact with the transparent head 2, and the big and the small springs 33, 34 are located behind the light emitter 32 to correspond to the positive and the negative electrodes, respectively, of the battery 35. Due to a spring force applied by the big spring 33 on the battery 35 to push the latter backward, the small spring 34 is normally prevented from electrically contacting with the bar-shaped negative electrode of the battery 35. And, the switch 4 is connected to the barrel 1 by screwing the fixing seat 41 to the rear end of the barrel 1 with a front-end surface of the movable rod 42 normally pressed against a rear-end surface of the battery 35. FIG. 2 is a sectional view of the assembled selector pen 10, wherein the light-emitting means 3 is not electrically made to emit light.
For the selector pen 10 to emit light, simply turn the cap 43 in a predetermined direction, so that the gear 422 received in the second recess 432 of the cap 43 is brought to rotate. At this point, the external screw thread 421 of the movable rod 42 is guided by the internal screw thread 413 of the fixing seat 41 to move forward, bringing the movable rod 42 to push against the battery 35 and accordingly compress the big spring 33. At this point, the bar-shaped negative electrode of the battery 35 is gradually moved forward to eventually contact the small spring 34 to make the light emitter 32 for the latter to emit light, as shown in FIG. 3. When the cap 43 is turned reversely, the movable rod 42 is brought to move backward and the light emitter 32 is turned off, accordingly, as shown in FIG. 2.
The above-described conventional selector pen 10 has the following disadvantages in its structure and operation:
1. The cap 43 includes a stepped internal space providing three recesses of different inner diameters. The middle one of the three recesses is configured to receive the gear 422, making it difficult and time-consuming to manufacture components for the switch 4.
2. Due to the switch 4 that is difficult and time-consuming to manufacture, the selector pen 10 is produced at increased cost.
3. When the cap 43 is turned clockwise or counterclockwise relative to the barrel 1 to turn on or off the light-emitting means 3, the internal and the external screw threads 413 and 421, due to their very delicate structure and therefore insufficient supporting pressure, tend to slip relative to one another, causing the switch 4 to lose its intended control function.
4. The switch 4 is not designed with means for actually defining exact number of turns of the switch 4 in order to turn on or off the light-emitting means 3. When the cap 43 is overly turned, for example, when the battery 35 is exhausted, the screw threads 413 and 421 tend to slip relative to one another or even break.
It is therefore tried by the inventor to develop a selector pen that has improved but simplified switch structure to eliminate the above-mentioned disadvantages existing in the conventional selector pen.
A primary object of the present invention is to provide a selector pen for touch screen, on which a simplified switch is provided to turn on or off a light-emitting means mounted in a barrel of the selector pen, so that the selector pen could be manufactured at lowered cost and effectively emit light when necessary.
To achieve the above and other objects, the selector pen for touch screen of the present invention mainly includes a barrel, a transparent head connected to a front end of the barrel, a light-emitting means mounted in the barrel to emit light that passes through the transparent head to illuminate a dim environment near the touch screen, and a switch rotatably connected to a rear end of the barrel to turn on or off the light-emitting means. The switch includes a base defining a non-circular insertion hole, a movable rod being fixedly received in the insertion hole of the movable rod and having an inclined top formed into a spiral guide surface, and a cap being rotatably covered onto the base and having an internal projection. When the cap is turned, the projection slides along the spiral guide surface to gradually depress the movable rod for the same to electrically make the light-emitting means.
The switch has simplified structure to enable lowered manufacturing cost of the selector pen, and the spiral guide surface defines a definite range of turning for the cap to avoid the problem of insufficiently or overly turned switch.